EP-A-0 338 553 discloses a scale for rail-supported vehicles comprising a frame for receiving rails and force measuring devices for determining vertical forces acting onto the rails. The frame comprises longitudinal girders arranged in parallel to the rails and lateral girders supporting the rails and resting on the longitudinal girders with the force measuring devices arranged between the rails and the longitudinal girders. Such a complex design is subject to errors in measurement due to strains and twisting of the girders when loaded and warmed up by sun radiation.
The German Laid Open Patent Publication 29 24 190 discloses an apparatus for determining presence and/or the weight of rail-supported vehicles using a piezo-electric force transducer arranged below the rail between the base thereof and a sleeper with the transducer being mounted in a support plate arranged therebetween. Force introduction to the transducer is rather inaccurate without any mechanical lateral compensation and temperature compensation.
U.S. Pat. No. 4,644,805 discloses a force measuring device comprising a pot-type housing having arranged therein a piston forming an annular gap with peripheral inner surfaces of the recess of said housing, said gap being filled with elastomeric material strongly adhering to surfaces in contact therewith and filling a bottom space in said housing, a pressure transducer being in contact with said elastomeric material.
The EP-A-0 281 640 discloses an apparatus for weighing of rail-supported vehicles. The rails are supported in the region of the weighing apparatuses via support members on measuring bars resting on sleepers with force transducers being arranged at the measuring bars. Measuring signals of one or several of the transducers may be added during weighing.
U.S. Pat. No. 4,465,151 discloses a weigh station including a remote controller receiving in a wireless transmission weighing signals denoting axle loadings of passing vehicles.